1. FIELD OF THE INVENTION
The present invention relates to passive load support devices and more particularly it relates to a passive load support cradle having a semi-active constituent in its construction which allows load equalization when a number of similar cradles are utilized for supporting a load. Still more particularly, the cradles of the present invention are used in multiples to support the weight of large structures as they are being disassembled from the bottom while the load of the structure is alternately lifted by jacks and then supported by the cradles.
2. DESCRIPTION OF THE PRIOR ART
The present invention was designed for use during the dismantling of large gas holders weighing in excess of 3,000 tons. The gas holders are in the form of a vertical cylinder approximately 400 feet high and 250 feet in diameter supported by a multiplicity of columns disposed around the periphery of the enclosure shell. The dismantling procedure consists of lifting the gas holder enclosure by hydraulic jacks disposed at every other one of the support columns. The alternate columns are cut off at the bottom along with a portion of the adjacent shell of the gas holder enclosure so the jacks can be fitted under the columns to lift the weight of the holder. When the holder has been lifted, the remaining alternate columns are cut off slightly higher than the height of the support cradles of the present invention whereby the holder structure can be lowered onto the cradles disposed at every other column around the gas holder between the jacks. These cradles then carry the load until the support columns and adjacent enclosure shell where each of the jacks are disposed can be further cut away, approximately the extension length of the jacks, and the jacks reactivated to again lift the structure. Then, the columns, and adjacent enclosure shell at each of the support cradles and the lower periphery of the gas holder is removed approximately equal to the amount of the stroke of the jacks. The jacks are then lowered the length of their stroke until the holder again rests on the cradles. The process can be repeated until the whole gas holder has been disassembled from the bottom and the remaining structure has been lowered close enough to the ground whereby it can be dismantled by other means.
The problem that needed to be solved occurs when the tank is lowered by the jacks onto the support cradles. With the heavy weight and inexact methods utilized to cut off the bottoms of the columns, it is necessary to provide a means whereby it can be assured that each of the support cradles is carrying nearly an equal share of the weight of the whole tank and performs its function of supporting one of the columns. If the columns are cut off by acetylene gas torches resulting an uneven surfaces, the problem is exacerbated. It is necessary to provide a cradle which can accommodate a possibly uneven cut without the necessity of accurately machining the bottom of each of the cut off columns before proceeding to lower the load onto the cradles.
In view of this unique engineering problem, there is no known prior art to the cradles of the present invention except for completely passive, inert support blocks.